1. Field of the Invention
The present invention relates in general to the field of extruders.
2. Description of Related Art
Machines for extruding, particularly those for extruding randomly shaped cornmeal snacks, include a random extruder assembly for shaping the snacks. For example, one type of randomly shaped cornmeal snacks sold under the trademark CHEETOS® is capable of being extruded from this extruder. CHEETOS® are but one brand of randomly shaped snacks that have been fabricated from extruders like this. FIG. 1 shows a conventional extruder machine 101 having a hopper assembly 103, a conveyer assembly 105, and an extruding assembly 107. Furthermore, extruding assembly 107 includes a rotor assembly 109, a stator assemble 111, and an auger assembly 113.
Referring now also to FIG. 2 in the drawings, a cross sectional view of conventional extruder machine 101 is illustrated. Material to be extruded, usually cornmeal with selected moisture content, is fed by auger assembly 113 from hopper assembly 103 to the extruder zone 115.
Referring now also to FIG. 3 in the drawings, a larger cross sectional view of conventional extruder machine 101 is illustrated. Extruding assembly 107 includes rotor assembly 109, stator assembly 111, and a servicing distance 117. Servicing distance 117 is the spacing between the rotor assembly 109 and the stator assembly 111. Servicing distance 117 is varied by moving the rotor assembly 109 in relation to the stator assembly 111. Typically while the machine 101 is serviced the servicing distance 117 is no more than a few inches. The servicing distance 117 allows a technician to maintain both the stator assembly 111 and the rotor assembly 109. Due to the servicing distance 117 having a limited amount of travel all tooling for maintenance to rotor assembly 109 and stator assembly 111 are limited in travel and therefore it is time consuming to remove a significant number of fasteners for maintenance of rotor assembly 109 and stator assembly 111.
Servicing distance 117 is minimized during operation of machine 101 to a very close gap of typically seventy thousands of an inch. Rotor assembly 109 rotates typically at six hundred rotations per minute. Both the rotor assembly 109 and the stator assembly 111 are heated and remain heated during operation of machine 101. As the cornmeal is expelled from the very close gap between rotor assembly 109 and stator assembly 111 the cornmeal twists and expands before falling on conveyer assembly 105.
Referring now also to FIG. 4 in the drawings, a perspective view of rotor assembly 109 and to FIG. 5 in the drawings, an exploded view of rotor assembly 109, both are illustrated. Rotor assembly 109 includes a rotor coupling 141 secured to a rotor base 145 by rotor base set screws 149. Located between rotor coupling 141 and rotor base 145 is a dowel pin 143. A die plate 153 is coupled to rotor base 145 by socket cap screws 157. Die plate 153 is typically made of bronze. Bronze has been the material of choice for the die plate because of the thermal properties of bronze. Socket cap screws 157 are located on the back side of the die plate 153 to prevent the extruding material from filling the screw head cavity. Die fingers 161 are located in openings in rotor base 145 and die plate 153 and secured by a press fit between die fingers 161 and rotor base 145. Press fit is a light press between ½ to 1/1000 press. Die fingers 161 are fabricated from rectangular cold rolled 303 stainless steel bars. A cutter holder 165 is clamped to rotor base 145 by tightening clamping bolt 169. External cutter 174 is coupled to cutter holder 165 by cutter screw 179. Replacing the external cutters is a time consuming task because of the alignment the external cutters 174 require. Since the cutter holder 165 is clamped to the rotor base 145 considerable time is required to align the external cutters 174. Another design flaw results in broken cutter holders 165 by over tighten the bolt 169. A plug 183 is coupled to rotor base 145 by a plug set screw 185 thereby sealing the center of rotor assembly 109. Rotor coupling set screws 189 are used to couple rotor assembly 109 to machine 101.
Die fingers 161 wear out quickly due to the friction of the corn meal and to acids, starches, and moisture contained in the corn meal. The normal life of the die fingers 161 is 350 to 400 hours of operation. Approximately two hours are required to replace the three die fingers 161. The considerable down time results from being forced to remove the rotor base 145. Removal of the rotor base 145 is necessary because the die fingers 161 can only be removed from the rotor base 145 when the rotor base 145 is not installed. Additionally the die plate 153 cannot be replaced without removal of the rotor base 145 because of the location of the socket cap screws 157. Additional down time occurs because of the time required to realign the rotor assemble 109 after replacing the die fingers 161 and the limited access to the rotor assembly 109 in the servicing distance 117. Additionally the preferred method to remove the worn die fingers 161 from the rotor base 145 consist of hammering the worn die fingers 161 out of the rotor base 145 to overcome the press fit. If a mechanic slips and strikes the rotor base 145 instead of the die fingers 161 then the rotor base 145 may be damaged by the errant blow.
Thus, there exists significant room for improvement in the art for overcoming these and other shortcomings of conventional extruder machine for extruding randomly shaped snacks.
While the assembly of the present application is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular embodiment disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present application as defined by the appended claims.